You want to ensure that a customer order is only processed once. Which of the following approaches would you use?

Using the Idempotency-Key header to the order ID is an effective way to ensure that a customer order is processed only once. When you include this key in your API request, it allows the Stripe system to recognize repeated requests with the same key as duplicates. Therefore, even if a customer accidentally sends multiple requests for the same order, Stripe will only process the first request and return the same response for any follow-up requests that include that Idempotency-Key. This mechanism protects against double processing and ensures the integrity of the transaction.

While unique order IDs can help identify transactions distinctly, they do not prevent the same order from being submitted multiple times. Likewise, a transaction confirmation email provides an acknowledgment of the order but does not prevent subsequent requests from being processed. Lastly, a customer verification call adds a level of assurance but does not inherently prevent duplicate processing and could be cumbersome in terms of operational efficiency. The use of the Idempotency-Key header strikes a balance between technical reliability and ease of customer experience.